The invention relates to novel cyclohexane derivatives of the formula I 
in which
Y is alkyl or alkoxy having 1 to 10 carbon atoms which is unsubstituted or at least monosubstituted by halogen up to perhalo, is alkenyl or alkenyloxy having 2 to 10 carbon atoms which is unsubstituted or at least monosubstituted by xe2x80x94CN, xe2x80x94CF3 or xe2x80x94F, or is xe2x80x94CN, xe2x80x94F, xe2x80x94OCHF2, xe2x80x94OCF3, xe2x80x94OCHFCF3 or xe2x80x94OCF2CF3,
one of X1 and
X2 is CF3, CHF2, CH2F, OCHF2, OCF3, SF5 or an alkyl radical having 2 to 10 carbon atoms which is monosubstituted or polysubstituted by fluorine or chlorine, and one of X1 or X2 in each cyclohexane ring is H,
R1 is H, an alkyl or alkenyl radical having 1 to 12 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen, where one or more non-adjacent CH2 groups in these radicals may also, in each case independently of one another, be replaced by 
A1 and A2, independently of one another, are
a) a trans-1,4-cyclohexylene radical, in which, in addition, one or more, preferably up to two, non-adjacent CH2 groups may be replaced by xe2x80x94Oxe2x80x94 and/or xe2x80x94Sxe2x80x94,
b) a 1,4-phenylene radical, in which, in addition, one or two CH groups may be replaced by N,
c) a radical from the group consisting of 1,4-bicyclo[2.2.2]-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, deca-hydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphthalene-2,6-diyl,
d) 1,4-cyclohexenylene,
where the radicals a), b) and d) may be substituted by CN, Cl or F, e.g., 0-4 times,
Z1, Z2 are each, independently of one another, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94,
and Z3xe2x80x94CH2Oxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CF2CF2xe2x80x94CF2Oxe2x80x94, xe2x80x94OCF2xe2x80x94 or a single bond,
n and m, independently of one another, are 0, 1, 2 or 3,
and
p is 0, 1, 2 or 3,
where
m+n+p is 1, 2, 3 or 4.
The invention also relates to the use of the compounds of the formula I as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements which contain the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of aligned phases DAP or ECB (electrically controlled birefringence) or the effect of dynamic scattering.
The substances employed hitherto for this purpose all have certain disadvantages, for example inadequate stability to the action of heat, light or electric fields, or unfavorable elastic and/or dielectric properties.
Similar compounds have already been disclosed in DE 19723276. However, this document only relates to compounds having axial F, Cl or CN, which are not covered by the present application. The laterally substituted cyclohexane derivatives covered by DE 3510432 preferably have equatorially arranged substituents. However, the subject-matter of the present application differs through the nature of the substituents.
The invention had the object of finding novel stable liquid-crystalline or mesogenic compounds having negative or low positive dielectric anisotropy which are suitable as components of liquid-crystalline media, in particular for TFT and STN displays.
It has now been found that the compounds of the formula I are eminently suitable as components of liquid-crystalline media. They can be used to obtain stable liquid-crystalline media, in particular suitable for TFT or STN displays. The novel compounds are distinguished, in particular, by high thermal stability, which is advantageous for a high holding ratio, and exhibit favorable clearing point values. Preferred compounds of the formula I have negative dielectric anisotropy and are therefore particularly suitable for displays based on the effect of deformation of aligned phases.
The provision of compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable from various applicational points of view for the preparation of liquid-crystalline mixtures.
The compounds of the formula I have a broad range of applications. Depending on the choice of substituents, these compounds may serve as base materials of which liquid-crystalline media are predominantly composed; however, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compound in order, for example, to modify the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimise its threshold voltage and/or its viscosity. The meaning of the formula I covers all isotopes of the chemical elements bound in the compounds of the formula I. The meaning of the formula I likewise covers both enantiomers of the respective compounds of the formula I. In enantiomerically pure or enriched form, the compounds of the formula I are also suitable as chiral dopants and in general for achieving chiral mesophases. One of ordinary skill can, with routine experimentation, determine the characteristics and properties needed to optimize the compounds and mixtures for use in these and other displays, as is wholly conventional in the art.
In the pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in a temperature range which is favourably located for electro-optical use. They are stable chemically, thermally and to light.
The invention thus relates to the compounds of the formula I and to the use of these compounds as components of liquid-crystalline media. The invention furthermore relates to liquid-crystalline media having a content of at least one compound of the formula I and to liquid-crystal display elements, in particular electro-optical display elements, which contain media of this type.
Above and below, n, m, p, R1, X1, X2, Z1, Z2, Z3, A1 A2 and Y are as defined above, unless expressly stated otherwise. If the radical X1 occurs more than once, it may adopt identical or different meanings. The same applies to X2, A1, A2, Z1, Z2 and Z3.
For reasons of simplicity, Cyc below denotes a 1,4-cyclohexylene radical, Che denotes a 1,4-cyclohexenylene radical, Dio denotes a 1,3-dioxane-2,5-diyl radical, Dit denotes a 1,3-dithiane-2,5-diyl radical, Phe denotes a 1,4-phenylene radical, Pyd denotes a pyridine-2,5-diyl radical, Pyr denotes a pyrimidine-2,5-diyl radical and Bco denotes a bicyclo[2.2.2]octylene radical, where Cyc and/or Phe may be unsubstituted or monosubstituted or polysubstituted by Cl, F or CN.
W denotes the following structural unit: 
in which p, X1, X2, X3 and Z2 are as defined above.
Formula I thus encompasses, i.a., compounds of the sub-formula Ia:
R1xe2x80x94Wxe2x80x94Yxe2x80x83xe2x80x83Ia
compounds of the sub-formulae Ib, Ic and Id:
R1xe2x80x94Wxe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ib
Rxe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ic
R1xe2x80x94A1xe2x80x94Z1xe2x80x94Wxe2x80x94Yxe2x80x83xe2x80x83Id
compounds of the sub-formulae Ie to Ii:
R1xe2x80x94Wxe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ie
R1xe2x80x94Wxe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83If
xe2x80x83R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ig
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ih
R1xe2x80x94A1xe2x80x94Z1xe2x80x94Wxe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ii
and compounds of the sub-formulae Ij to Ir:
R1xe2x80x94Wxe2x80x94A2xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ij
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ik
R1xe2x80x94Wxe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83II
R1xe2x80x94Wxe2x80x94A2xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Im
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83In
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Io
R1xe2x80x94Wxe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ip
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Iq
R1xe2x80x94A1xe2x80x94Z1xe2x80x94Wxe2x80x94A2xe2x80x94Z2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Ir
Of these, particular preference is given to those of the sub-formulae Ia, Ib, Id, Ie, If, Ih, Ii and Ij.
The preferred compounds of the sub-formula Ib include those of the sub-formulae Iba and Ibb:
R1xe2x80x94W-Phe-Yxe2x80x83xe2x80x83Iba
R1xe2x80x94W-Cyc-Yxe2x80x83xe2x80x83Ibb.
The preferred compounds of the sub-formula Ic include those of the sub-formulae Ica and Icb:
R1xe2x80x94Wxe2x80x94Z3-Phe-Yxe2x80x83xe2x80x83Ica
R1xe2x80x94Wxe2x80x94Z3-Cyc-Yxe2x80x83xe2x80x83Icb.
The preferred compounds of the sub-formula Id include those of the sub-formulae Ida and Idb:
R1-Dio-Z1xe2x80x94Wxe2x80x94Yxe2x80x83xe2x80x83Ida
R1-Cyc-Z1xe2x80x94Wxe2x80x94Yxe2x80x83xe2x80x83Idb.
The preferred compounds of the sub-formula Ie include those of the sub-formulae Iea to Ieg:
R1xe2x80x94W-Cyc-Cyc-Yxe2x80x83xe2x80x83Iea
R1xe2x80x94W-Cyc-Phe-Yxe2x80x83xe2x80x83Ieb
R1xe2x80x94W-Phe-Phe-Yxe2x80x83xe2x80x83Iec
R1xe2x80x94W-Pyd-Phe-Yxe2x80x83xe2x80x83Ied
R1xe2x80x94W-Phe-Cyc-Yxe2x80x83xe2x80x83Iee
R1xe2x80x94W-Dio-Phe-Yxe2x80x83xe2x80x83Ief
R1xe2x80x94W-Pyr-Phe-Yxe2x80x83xe2x80x83Ieg.
Of these, those of the formulae Iea, Ieb, Iec and Iee are particularly preferred.
The preferred compounds of the sub-formulae If include those of the sub-formulae Ifa to Ifg:
R1xe2x80x94W-Cyc-Z3-Cyc-Yxe2x80x83xe2x80x83Ifa
R1xe2x80x94W-Cyc-Z3-Phe-Yxe2x80x83xe2x80x83Ifb
R1xe2x80x94W-Phe-Z3-Phe-Yxe2x80x83xe2x80x83Ifc
R1xe2x80x94W-Pyr-Z3-Phe-Yxe2x80x83xe2x80x83Ifd
R1xe2x80x94W-Pyd-Z3-Phe-Yxe2x80x83xe2x80x83Ife
R1xe2x80x94W-Cyc-CH2-CH2-Phe-Yxe2x80x83xe2x80x83Iff
R1xe2x80x94Wxe2x80x94A2xe2x80x94CH2CH2-Phe-Yxe2x80x83xe2x80x83Ifg.
The preferred compounds of the sub-formula Ig include those of the sub-formulae Iga to Igb:
R1xe2x80x94Wxe2x80x94Z3-Cyc-Cyc-Yxe2x80x83xe2x80x83Iga
R1xe2x80x94Wxe2x80x94CH2CH2xe2x80x94A2xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Igb
R1xe2x80x94Wxe2x80x94Z3-Cyc-Phe-Yxe2x80x83xe2x80x83Igc
R1xe2x80x94Wxe2x80x94OCOxe2x80x94A2-Phe-Yxe2x80x83xe2x80x83Igd
R1xe2x80x94Wxe2x80x94Z3-Phe-Phe-Yxe2x80x83xe2x80x83Ige
R1xe2x80x94Wxe2x80x94Z3-Pyr-A2xe2x80x94Yxe2x80x83xe2x80x83Igf
R1xe2x80x94Wxe2x80x94Z3-Pyd-A2xe2x80x94Yxe2x80x83xe2x80x83Igg
xe2x80x83R1xe2x80x94Wxe2x80x94Z3-Dio-A2xe2x80x94Yxe2x80x83xe2x80x83Igh.
Of these, those of the sub-formulae Iga, Igb, Igc and Ige are particularly preferred.
The preferred compounds of the sub-formula Ih include those of the sub-formulae Iha to Ihe:
R1xe2x80x94Wxe2x80x94CH2CH2-Phe-Z3xe2x80x94A2xe2x80x94Yxe2x80x83xe2x80x83Iha
R1xe2x80x94Wxe2x80x94COOxe2x80x94A2xe2x80x94Z3-Phe-Yxe2x80x83xe2x80x83Ihb
R1xe2x80x94Wxe2x80x94Z3-Cyc-Z3-Cyc-Yxe2x80x83xe2x80x83Ihc
R1xe2x80x94Wxe2x80x94Z3-Phe-Z3-Phe-Yxe2x80x83xe2x80x83Ihd
R1xe2x80x94Wxe2x80x94CH2CH2-Cyc-Z3-Phe-Yxe2x80x83xe2x80x83Ihe.
The preferred compounds of the sub-formula Ii include those of the sub-formulae Iia to Iie:
R1xe2x80x94CH2CH2xe2x80x94W-Phe-Yxe2x80x83xe2x80x83Iia
R1-Dio-W-Phe-Yxe2x80x83xe2x80x83Iib
R1-Phe-W-Cyc-Yxe2x80x83xe2x80x83Iic
R1-Cyc-W-Cyc-Yxe2x80x83xe2x80x83Iid
R1-Dio-CH2CH2xe2x80x94W-Cyc-Yxe2x80x83xe2x80x83Iie.
The preferred compounds of the sub-formulae Ij to Ir include those of the sub-formulae Is to Iz:
R1xe2x80x94Wxe2x80x94A2-Cyc-Cyc-Yxe2x80x83xe2x80x83Is
R1xe2x80x94Wxe2x80x94A2-Cyc-Phe-Yxe2x80x83xe2x80x83It
R1xe2x80x94Wxe2x80x94A2xe2x80x94CH2CH2xe2x80x94A2-Phe-Yxe2x80x83xe2x80x83Iu
R1xe2x80x94Wxe2x80x94Z3-Cyc-Z3xe2x80x94A2-Phe-Yxe2x80x83xe2x80x83Iv
R1xe2x80x94W-Phe-Phe-Phe-Yxe2x80x83xe2x80x83Iw
R1xe2x80x94W-Phe-Z3xe2x80x94A2-Phe-Yxe2x80x83xe2x80x83Ix
R1xe2x80x94Wxe2x80x94A2-Phe-Z3-Phe-Yxe2x80x83xe2x80x83Iy
R1xe2x80x94Wxe2x80x94Z3xe2x80x94A2-Cyc-Z3-Phe-Yxe2x80x83xe2x80x83Iz.
Y is preferably xe2x80x94CN, F, OCF3, straight-chain alkyl or alkoxy having 1 to 10 carbon atoms, alkenyl or alkenyloxy having 2 to 10 carbon atoms, in particular CN, F, alkyl, alkoxy or alkenyl. Very particularly preference is given to alkyl or alkoxy.
The preferred meaning of X1 and X2 is CF3, CHF2, CH2F, OCHF2 or OCF3, in particular CF3.
In the compounds of the formulae above and below, R1 is preferably straight-chain alkyl having 1 to 10 carbon atoms or alkenyl having 2 to 10 carbon atoms, furthermore preferably alkoxy having 1 to 10 carbon atoms.
A1 is preferably Phe, Cyc, Che, Pyd, Pyr or Dio, in particular Cyc or Dio. The compounds of the formula I preferably contain not more than one of the radicals Bco, Pyd, Pyr, Dio or Dit.
Preference is also given to compounds of the formula I and of all sub-formulae in which Al is 1,4-phenylene which is monosubstituted or disubstituted by F or CN.
A1 is preferably 
n is preferably 0 or 1, particularly preferably 0. m and p are preferably 0,1 or 2, particularly preferably 0 or 1. Z1, Z2 and Z3 are preferably, independently of one another, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond, particularly preferably a single bond or xe2x80x94CH2xe2x80x94CH2xe2x80x94.
Preference is given to compounds of the formula I in which R1 and Y are simultaneously alkyl having 1 to 10 carbon atoms, while n is 0 and m is 1.
Particular preference is furthermore given to compounds of the formula I that are characterised in that R1 is straight-chain alkyl or alkoxy having 1 to 10 carbon atoms or alkenyl having 2 to 10 carbon atoms, and Y is alkyl having 1 to 10 carbon atoms, alkenyl having 2 to 10 carbon atoms, xe2x80x94CN, xe2x80x94F, xe2x80x94CHF2 or xe2x80x94OCF3.
Particular preference is given to compounds of the formula I in which X1 or X2 has the same meaning if they occur more than once.
The 1,4-cyclohexenylene group preferably has the following structures: 
The following group of compounds of the sub-formulae I1 to I15 represents preferred embodiments of the invention: 
in which n, m, R1, Z1, Z2, Z3, A1, A2 and Y are as defined above. In the formulae 17 to I15, Y is preferably alkyl, alkoxy or oxaalkyl having 1-10 carbon atoms or alkenyl having 2 to 10 carbon atoms.
Particular preference is furthermore given to the compounds of the formulae I16 to I37 from the following group: 
in which R1, Z1, Z2, Z3 and Y are as defined above, L1, L2 and L3 are each, independently of one another, F or H, L1 and L2 preferably being F and L3 preferably being H.
If R1 in the formulae above and below is an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.
Oxaalkyl, e.g., as R1, is preferably straight-chain 2-oxapropyl (=methoxy-methyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.
If R1 is an alkyl radical in which one CH2 group has been replaced by xe2x80x94CHxe2x95x90CHxe2x80x94, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it is in particular vinyl, prop-1- or prop-2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, 4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, or dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.
If R1 is an alkyl radical in which one CH2 group has been replaced by xe2x80x94Oxe2x80x94and one has been replaced by xe2x80x94COxe2x80x94, these are preferably adjacent. These thus contain an acyloxy group xe2x80x94COxe2x80x94Oxe2x80x94 or an oxycarbonyl group xe2x80x94Oxe2x80x94CO. These are preferably straight-chain and have 2 to 6 carbon atoms.
Accordingly, they are in particular acetoxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl, 3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxycarbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl or 4-(methoxycarbonyl)butyl.
If R1 is an alkyl radical in which one CH2 group has been replaced by unsubstituted or substituted xe2x80x94CHxe2x95x90CHxe2x80x94 and an adjacent CH2 group has been replaced by CO or COxe2x80x94O or Oxe2x80x94CO, this may be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms. Accordingly, it is in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxy-hexyl, 7-acryloyloxyheptyl, 8-acryloyloxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, 1-methacryoyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryloyloxynonyl.
If R1 is an alkyl or alkenyl radical which is monosubstituted by CN or CF3, this radical is preferably straight-chain and the substitution by CN or CF3 is in the xcfx89-position.
If R1 is an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain, and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resultant radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the xcfx89-position.
Compounds of the formula I having a branched wing group R1 may occasionally be of importance owing to better solubility in the conventional liquid-crystalline base materials, but in particular as chiral dopants if they are optically active. Smectic compounds of this type are suitable as components of ferroelectric materials.
Branched groups of this type generally contain not more than one chain branch. Preferred branched radicals R1 are isopropyl, 2-butyl (=1-methyl-propyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl (=3-methyl-butyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methyl-pentoxy, 3-methylpentoxy, 2-ethylhexyloxy, 1-methylhexyloxy and 1-methylheptyloxy.
Formula I covers both the racemates of these compounds and the optical antipodes, and mixtures thereof. Trans isomers are preferred. Resolution, e.g., separation from diastereomeric mixtures, is conventional. See Kirsch and Bremer, Angew. Chem., 112, 2000, 4384 and Handbook of Liquid Crystals (ed. Demus et al., Wiley VCH Weinheim 1998).
Of these compounds of the formula I and the sub-formulae, preference is given to those in which at least one of the radicals present therein has one of the preferred meanings indicated.
In the compounds of the formula I, preference is given to the stereo-isomers in which the rings Cyc and piperidine are trans-1,4-disubstituted. Those of the above-mentioned formulae which contain one or more groups Pyd, Pyr and/or Dio in each case cover the two 2,5-positional isomers.
Some very particularly preferred smaller groups of compounds of the formula I are those of the sub-formulae I38 to I47: 
in which R1 is as defined above, and Yxe2x80x2 is alkyl, alkoxy, alkenyl or alkenyloxy.
Very particularly preferred compounds from this group are those of the formulae I38, I39, I40, I44 and I45.
The compounds of the formula I are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for the said reactions.
Use can also be made here of variants which are known per se, but are not mentioned here in greater detail.
The synthesis of the axially fluorinated compounds of the formula I according to the invention can be achieved by using hydrogen fluoride under pressure or by means of amine/hydrogen fluoride adducts (for example A. V. Grosse, C. B. Linn, J. Org. Chem. 3, (1938) 26; G. A. Olah, M. Nojima, I. Kerekes, Synthesis, (1973) 779); G. A. Olah, X-Y. Li, Q. Wang, G. K. S. Prakash, Synthesis (1993) 693).
The compounds according to the invention can be prepared, for example, in accordance with the following reaction schemes: 
Esters of the formula I can also be obtained by esterification of corresponding carboxylic acids (or their reactive derivatives) using alcohols or phenols (or their reactive derivatives) or by the DCC method (DCC=dicyclohexylcarbodiimide).
The corresponding carboxylic acids and alcohols or phenols are known or can be prepared analogously to known processes.
Nitriles can be obtained by exchange of halogens with copper cyanide or alkali metal cyanide.
In a further process for the preparation of the compounds of the formula I in which Z1, Z2 or Z3 is xe2x80x94CHxe2x95x90CHxe2x80x94, an aryl halide is reacted with an olefin in the presence of a tertiary amine and in the presence of a palladium catalyst (cf. R. F. Heck, Acc. Chem. Res. 12 (1979) 146). Examples of suitable aryl halides are chlorides, bromides and iodides, in particular bromides and iodides. The tertiary amines necessary for the success of the coupling reaction, such as, for example, triethylamine, are also suitable as solvent. Examples of suitable palladium catalysts are the salts thereof, in particular Pd(II) acetate, with organic phosphorus(III) compounds, such as, for example, triarylphosphines. The process can be carried out in the presence or absence of an inert solvent at temperatures between about 0xc2x0 C. and 150xc2x0 C., preferably between 20xc2x0 C. and 100xc2x0 C.; suitable solvents are, for example, nitrites, such as acetonitrile, or hydrocarbons, such as benzene or toluene. The aryl halides and olefins employed as starting materials are in many cases commercially available or can be prepared by processes known from the literature, for example by halogenation of corresponding parent compounds or by elimination reactions on corresponding alcohols or halides.
In this way, stilbene derivatives, for example, can be prepared. The stilbenes can furthermore be prepared by reaction of a 4-substituted benzaldehyde with a corresponding phosphorus ylide by the Wittig method. However, tolans of the formula I can also be prepared by employing monosubstitued acetylene instead of the olefin (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171(1986)).
For the coupling of aromatic compounds, it is furthermore possible to react aryl halides with aryltin compounds. These reactions are preferably carried out with addition of a catalyst, such as, for example, a palladium(0) complex, in inert solvents, such as hydrocarbons, at high temperatures, for example in boiling xylene, under a protective gas.
Coupling reactions of alkynyl compounds with aryl halides can be carried out analogously to the process described by A. O. King, E. Negishi, F. J. Villani and A. Silveira in J. Org. Chem 43, 358 (1978).
Tolans of the formula I in which Z1 or Z2 is xe2x80x94Cxe2x89xa1Cxe2x80x94 can also be prepared by the Fritsch-Buttenberg-Wiechell rearrangement (Ann. 279, 319, 1984), in which 1,1-diaryl-2-haloethylenes are rearranged to give diarylacetylenes in the presence of strong bases.
Tolans of the formula I can also be prepared by brominating the corresponding stilbenes, followed by dehydrohalogenation. Use can be made here of variants of this reaction which are known per se, but are not mentioned here in greater detail.
Ethers of the formula I are obtainable by etherification of corresponding hydroxyl compounds, preferably corresponding phenols, where the hydroxyl compound is advantageously firstly converted into a corresponding metal derivative, for example into the corresponding alkali metal alkoxide or alkali metal phenoxide by treatment with NaH, NaNH2, NaOH, KOH, Na2CO3 or K2CO3. This metal derivative can then be reacted with the appropriate alkyl halide, alkyl sulfonate or dialkyl sulfate, advantageously in an inert solvent, such as, for example, acetone, 1,2-dimethoxyethane, DMF or dimethyl sulfoxide, or alternatively with an excess of aqueous or aqueous-alcoholic NaOH or KOH, at temperatures between about 20xc2x0 C. and 100xc2x0 C.
The starting materials are either known or can be prepared analogously to known compounds.
The compounds of the formula I can be obtained in enantiomerically pure form by conventional methods, preferably by chiral preparative HPLC.
The liquid-crystalline media according to the invention preferably comprise from 2 to 40, in particular from 4 to 30, components as further constituents besides one or more compounds according to the invention. These media very particularly preferably comprise from 7 to 25 components besides one or more compounds according to the invention. These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclo-hexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclohexanecarboxylic acid or of cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes, 1,4-biscyclohexylbenzenes, 4,4xe2x80x2-biscyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes, 1-cyclohexyl-2-biphenylylethanes, 1-phenyl-2-cyclohexylphenylethanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.
The most important compounds suitable as further constituents of media according to the invention can be characterised by the formulae 1, 2, 3, 4 and 5:
Rxe2x80x2xe2x80x94Lxe2x80x94Exe2x80x94Rxe2x80x3xe2x80x83xe2x80x831
Rxe2x80x2xe2x80x94Lxe2x80x94COOxe2x80x94Exe2x80x94Rxe2x80x3xe2x80x83xe2x80x832
Rxe2x80x2xe2x80x94Lxe2x80x94OOCxe2x80x94Exe2x80x94Rxe2x80x3xe2x80x83xe2x80x833
Rxe2x80x2xe2x80x94Lxe2x80x94CH2CH2xe2x80x94Exe2x80x94Rxe2x80x3xe2x80x83xe2x80x834
Rxe2x80x2xe2x80x94Lxe2x80x94Cxe2x89xa1Cxe2x80x94Exe2x80x94Rxe2x80x3xe2x80x83xe2x80x835
In the formulae 1, 2, 3, 4 and 5, L and E, which may be identical or different, are each, independently of one another, a divalent radical from the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl, and G is 2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.
One of the radicals L and E is preferably Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably comprise one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which L and E are selected from the group consisting of Cyc, Phe and Pyr and simultaneously one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which one of the radicals L and E is selected from the group consisting of Cyc, Phe and Pyr and the other radical is selected from the group consisting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which the radicals L and E are selected from the group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.
In a smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5, Rxe2x80x2 and Rxe2x80x3 are each, independently of one another, alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. This smaller sub-group is called group A below, and the compounds are referred to by the sub-formulae 1a, 2a, 3a, 4a and 5a. In most of these compounds, Rxe2x80x2 and Rxe2x80x3 are different from one another, one of these radicals usually being alkyl, alkenyl, alkoxy or alkoxyalkyl.
In another smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5, which is known as group B, Rxe2x80x3 is xe2x80x94F, xe2x80x94Cl, xe2x80x94NCS or xe2x80x94(O)iCH3xe2x88x92(k+l)FkCll, where i is 0 or 1, and k and l are 1, 2 or 3; the compounds in which Rxe2x80x3 has this meaning are referred to by the sub-formulae 1b, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b in which Rxe2x80x3 is xe2x80x94F, xe2x80x94Cl, xe2x80x94NCS, xe2x80x94CF3, xe2x80x94OCHF2 or xe2x80x94OCF3.
In the compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b, Rxe2x80x2 is as defined for the compounds of the sub-formulae 1a-5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.
In a further smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5, Rxe2x80x3 is xe2x80x94CN; this sub-group is referred to below as group C, and the compounds of this sub-group are correspondingly described by sub-formulae 1c, 2c, 3c, 4c and 5c. In the compounds of the sub-formulae 1c, 2c, 3c, 4c and 5c, Rxe2x80x2 is as defined for the compounds of the sub-formulae 1a-5a and is preferably alkyl, alkoxy or alkenyl.
Besides the preferred compounds of groups A, B and C, other compounds of the formulae 1, 2, 3, 4 and 5 having other variants of the proposed substituents are also customary. All these substances are obtainable by methods which are known from the literature or analogously thereto.
Besides the compounds of the formula I according to the invention, the media according to the invention preferably comprise one or more compounds selected from group A and/or group B and/or group C. The proportions by weight of the compounds from these groups in the media according to the invention are preferably
group A: from 0 to 90%, preferably from 20 to 90%, in particular from 30 to 90%
group B: from 0 to 80%, preferably from 10 to 80%, in particular from 10 to 65%
group C: from 0 to 80%, preferably from 5 to 80%, in particular from 5 to 50%,
the sum of the proportions by weight of the group A and/or B and/or C compounds present in the respective media according to the invention preferably being 5%-90% and in particular from 10% to 90%.
The media according to the invention preferably comprise from 1 to 40%, particularly preferably from 5 to 30%, of the compounds according to the invention. Preference is furthermore given to media comprising more than 40%, in particular from 45 to 90%, of compounds according to the invention. The media preferably comprise three, four or five compounds according to the invention.
The media according to the invention are prepared in a manner which is conventional per se. In general, the components are dissolved in one another, advantageously at elevated temperature. By means of suitable additives, the liquid-crystalline phases according to the invention can be modified in such a way that they can be used in all types of liquid-crystal display elements that have been disclosed hitherto. Additives of this type are known to the person skilled in the art and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be added for the preparation of colored guest-host systems or substances can be added to modify the dielectric anisotropy, the viscosity and/or alignment of the nematic phases.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight.
The entire disclosure of all applications, patents and publications, cited above, and of corresponding German application No. DE 100 313 82.5, filed Jun. 28, 2000, is hereby incorporated by reference.
m.p. denotes melting point, cl.p.=clearing point. Furthermore, C=crystalline state, N=nematic phase, Sm=smectic phase and I=isotropic phase. The data between these symbols represent the transition temperatures. xcex94n denotes optical anisotropy (589 nm, 20 C.) and xcex94xcex5 denotes the dielectric anisotropy (1 kHz, 20xc2x0 C.). The viscosity (mm2/sec) was determined at 20xc2x0 C.
xe2x80x9cConventional work-upxe2x80x9d means that water is added if necessary, the mixture is extracted with methylene chloride, diethyl ether or toluene, the phases are separated, the organic phase is dried and evaporated, and the product is purified by distillation under reduced pressure or crystallization and/or chromatography.
The following abbreviations are used: